package 集合.Map.HashMap.Test01;

import java.util.*;

public class HashMapTest01 {
    public static void main(String[] args) {
        Map map = new HashMap();
        map.put(null,null);
        System.out.println(map.size());
        map.put(null,100);
        System.out.println(map.size());
        System.out.println(map.get(null));

    }
}
